Internal combustion hammer



July 7, 1931. s. R. SAUNDERS 1,313,513

I I INTERNAL COMBUSTION HAMMER Filed Feb, 25. 1927 INVENTOR.

By fi 5W M A TTORNE Y.

20 the angular position of the Patented July 7, 1931 PATENT? OFFICE sum-um. n. saunnnns, or exam; BAY, wrscon'sm COMBUSTION Application filed February 25,1927. Serial No. rzop'm.

This invention relates to improvements in A floating piston is free in' the cylinder internal combustion hammers.

It is one of the primary objects of the in timing mechanism ina device of this kind. and to make such disposition of the parts that they will be free from all carbon trouble and will not be subject to the direct heat of the combustion chamber. It is my object also to devise an ignition timing mechanism for an 1 engine of this type which will necessarily leave the ignition circuit open when the engine piston is 'at rest. It is a further purpose to provide a new and improved means for utilizing the ignition timing mechanism to fix piston during its reciprocation in the cylinde I It is a further object of the invention to provide an improved anvil mounting which will relieve the frame structure of the hammer from shock when the tool is operating but is not in use. a

It is a further object of the invention to simplify manufacture and repair by designing a frame for the device in the form of only three separate castings'which are readily ma-' chined and may be assembled anddisassembled with greatfacility.

The drawin shows a vertical axial section through a device embodying this invention.

The frame of the machine includes an engine cylinder 1, the cylinder head 2, and a'base plate 3. The cylinder and cylinder head will noted to be provided with radial fins for cooling. I f

The three piece construction of the frame enables the use of different materials in the various parts; facilitates machining by rendering all parts of the several castings read- 7 at 4 and which extend through the entire frame in clamping engagement with the cylinder head and base plate at the ends thereof.

' piston skirt and seats upon a thrust member 12 plate into contact with the head in the 'sensethat it is not connected wlth any crank. The piston carries a hammer 6 which is centered co-axiallywithin the iston skirt and has a shank portion 7 extending through the piston head and upset at 8 into engagi- 'ment therewith. The piston is supported a compression spring 10 which is wound concentrically about the hammer and within the held in place by the thrust of spring 45 hereinafter to be described.

Durin piston reciprocation the hammer 6 acts at the end of each expansion stroke upon an anvil 13 which'has an axially slidable 'bearing in the closure 12 and is provided at- 14 with a head for engaging any tool which may be fitted into the device. By way of exemplifying one of the many tools WhlCh ma be operated with mechanism of this sort, .70

' have shown fragmentarily a rock drill 15 received through an aperture ,16 in the base rtion 14 of anvil 13 to receive therefrom the lmpact of the hammer 6. The base plate is preferably provided with an elongated bearing boss at 17 for the guidance of the tool.

The fuel supply for the engine may conveniently be carried on the tool in a fuel tank 19 formed integrally with the engine cylinder feasting 1 A duct from thetank, which is. not shown ecause it is a more or less standard construction, leads to the seat of air valve 20 and thereby carburets the air. admitted through said valve to the passage 21. Passage 21 opens into the transfer passage 22 which communicates between the cyllnder compression chamber 23 below the piston and the combustion chamber .24 above the piston. The piston is cut away at 25 to afford access from the transfer port to the combustion chamber when the piston is in its outermost position, as shown. In this position of=the piston the exhausti port 26 is uncovered and the expanding gases in the cylinder will be permitted to escape through exhaust pipe 27 which may, iii-desired, be arranged to deliver the gases to a central duct 28 in drill 15, whereby the pressure of exhaust gases-may be used to blow away dust and rock fragments from the drill point 29.

It will be understood that the engine operates on the usual two cycle principle, air being drawn into compression chamber 23 through passage 21 and valve 20 during the upward movement of the piston under the compression of spring 10. In passing the check valve 20 the air is carbureted and is also supplied with a certain amount of lubricant, which is preferably included in the fuel. During the. expansion stroke of the piston the charge in the compression chamber is compressed, and as soon as the inlet port at the upper end of transfer passage 22 is uncovered the incoming charge enters the combustion chamber under considerable pressure, while the burnt gases escape through the exhaust pipe, as above described.

A spark plug 30 is provided for ignition in the usual manner. The means for timing ignition is one of the most important features of the present invention. It will be noted that the base of the plug is grounded as usual and that the central electrode is exposed to receive connection with a source of electrical energy, such as a battery or the like. The other terminal of the battery is connected with the frame of the device through the timer mechanism. The exposed terminal 32 of the timer is adapted to receive the, electrical connection from the battery and is clamped centrally Within an insulating bushing 33 threaded to the cylinder casting. The inner end of this terminal is provided with a fixed contact 34. The plunger 35, spring-pressed toward the axis of the engine cylinder, carries a yieldably mounted contact 36 which is normally spaced a slight distance from fixed contact 34. It will be noted that the end of the plunger projects slightly into the cylinder and is there received into the cam groove 37 which is cut longitudinally in the exterior surface of the piston skirt.

The cam groove 37 serves a dual function. It is provided at 38 with a cam nose for pressing the cam follower 35 outwardly to engage contact 36 with contact 34. Its interaction with the cam follower operates moreover to secure the piston against rotation so that its cut-away portion 25 will invariably register with the inlet port as the piston reaches its extreme outward position. In this way the timing mechanism is employed to perform the additional'function of maintaining the piston in its proper adjustment.

It is particularly to be noted that the cam groove terminates below the piston rings 39. It will be obvious, therefore, that these rings protect the timing mechanism from carbon and also from the direct heat of gases in the combustion chamber. In fact, the incoming gases keep the timing mechanism at reasonable temperatures for practical operation. It will be understood that the details of the tim tected from the combustion chamber.

ing mechanism herein disclosed are comparatively unimportant. It is desired to emphasize the location of the timing mechanism at a point where it can be acted upon directly by the piston while remote from and pro- It will be obvious that other specific timer contact mechanisms may beemployed and that other positions for such mechanisms may be chosen without departing from the spirit or the purposes or accomplishments of this invention.

It will be noted that the cam nose portion 38 of the cam groove 37 is located. at the extreme end of the piston stroke with reference to the cam follower. That is to say, the cam nose is so disposed that during the compression stroke of the piston it will pass the cam follower. This arrangement has two advantages. In the first place, it gives a desirable timing advance and causes the spark plug to ignite the gases in the combustion chamber slightly in advance of the time when the piston reaches the end of its stroke. In the second place, the arrangement is such that when the engine is at rest the ignition circuit will always be broken. It will be obvious that if the cam nose were only engaged' with the timer cam in the uppermost position of the piston it would be necessary to have an extraneous switch to shut off the ignition, since the piston always occupies its uppermost position when the engine is at rest. In such an arrangement the operator would continuously lose his battery current through the spark plug with the device at rest if he should fail to cut off his switch upon stopping the engine.

The ignition circuit comp-rises a battery 50 grounded at 51 and connected with the timing terminal 32 through wire 52 which encircles the magnetic core 53. The contact 36, which is grounded at 54, closes the circuit noted when it is urged into contact with the contact 34 by means of the camnose 38. When this circuit is closed, the magnetic flux in magnet 53 induces a current in the circuit including wire 58 which encircles the magnet 53, spark plug 30, and ground connections 54 and 57. Since the compression spring 10 normally maintains the piston in the top of the cylinder, it is necessary to provide some means of actuating the piston in order to draw in a charge and operate the timer to set the engine in motion. This is done through the simple expedient of a starting plunger 40' guided in a tubular extension 41 of cylinder head casting 2 and provided with a terminal valve head at 42 adapted normally to seal the opening through which the plunger operates. The plunger is normally maintained elevated by a compression spring 42. It is shown in the drawing fragmentarily, but it will be understood to be of such length as to be adapted to force the piston to the extremelower charge therein is ignited and the operation becomes automatic.

This type of engine being already known, it is only necessary to explain briefly thatduring engine operation .each expansion stroke of the piston compresses spring 10 and causes hammer 6 to impact the anvil which transmits the impact to the tool. As soon as the piston clears the exhaust port the pressure in the combustion chamber isrelieved and the spring 10 forces the piston upwardly on its compression stroke to compress the fresh charge admitted through the transfer passage 22.

As the piston nears the top of its stroke the timing mechanism causes a spark to pass between the electrodes of spark plug 30, thereby igniting the fresh charge. The compression of gases in the combustion chamber, as well as the expansion of such gases which takes place inoignition, cushions the upward movement of the piston. The downward movement, however, is uncushioned except as hereinafter disclosed. a

It has been observed that devices of this general character have been subject tobreakage in actual practice. I have found that such breakage is due to crystallization of the portions of the base plate 3 which immediately surround the drill or other-tool mounted .therein, and I have further found that the crystallization and consequent breakage are not due to any cause inherently connected with the operation of the tool but are rather due to the operation of the engine while the tool is idle.

It will be obvious that when the tool is firmly engaged with the work the entire impact of the hammer is transmitted from the anvil directly to the tool and thence directly 7 to the work. Under such circumstances the frame of the machine is'wholly relieved from shock, and if theengine were only in operation'during the period of actual use of the tool no shock absorbing means would be necessary. When, however, the tool is lifted from the work while the engine is in operation there is nothing to absorb the hammer blow except the frame of the machine itself, and under such treatment the frame soon becomes crystallized and breaks. I have discovered that it is possible to avoid this practical difficulty by the provision of a heavy spring at 45. This spring is interposed between the base plate 28 and the anvil head 14 and serves to maintain the anvil normally elevated against a fibrous gasket 46. It might reasonably be expected that such a spring would deaden the force of the hammer in its action through the tool upon the work but suchis not the case. When the tool is in use the actual movement of the tool is very slight, and under such circumstances the impact of the hammer is transmitted through the tool practically undeadened by spring 45. If, however, the tool .is lifted from the work and is thus incapable of absorbing suchimpact, the subsequent operation of the engine will only cause the anvil to compress spring 45, thereby relieving the frame of the device from the shock. The shock of the returning of the anvil subse-. quent to the slight compression which is 00- casioned in spring 45 is taken by the gasket 46.

It will be obvious from the foregoing that I have in many practical ways improved the arrangement of parts and structure of a tool of this character. As a result, sticking of the mechanism and breaka e of the parts are avoided and the manufacturing cost is 'reduced. It will be apparent, therefore, that the objects of the invention are satisfied bythe disclosure.

I claim: 1. In a device of the character described,

the combination with a cylinder having a port and a floating piston reciprocable there- 111 and provided with a bevelled portion adapted to registerwith said port in one position, of said piston, means for securing said piston against rotation during its reci rocation in said cylinder',whereby to maintain said bevelled portion in a position for registry with said port, said means comprising a timer control member in splined engagement with said piston.

2. In adevlce of the character described,

the combination with a cylinder having a port and a floating piston reciprocable therein: and provided with a bevelled portion adapted to register with said port in one position of said piston, of means for securing said piston against rotation during its reciprocation in said cylinder, whereby to main- 3. In a device of the character described, the'combination with a cylinder having a port and a floating piston reciprocal therein and having a predetermined portion formed for registry with the port of said cylinder in one positionof said piston, of a key device engaging said piston in splined relation .to

said cylinder whereby to secure said piston against rotation during its reciprocation and to ensure registry of said piston portion with said port, said key device comprising a timer actuating member in operative engagement With said piston and adapted to receive move- 5 Inent therefrom in the course of piston reciprocation.

SAMUEL R. SAUNDERS. 

